Hyperinsulinemia and insulin resistance is associated with low T3/T4 ratio in pre diabetic euthyroid pakistani subjects

ObjectiveTo investigate the relationship of thyroid hormones in glucose homeostasis in impaired glucose-tolerant subjects with normal thyroid functions.MethodsCross-sectional analysis was carried out in (n = 260) impaired glucose-tolerant (IGT) and normal glucose-tolerant (NGT) subjects. Thyrotropin (TSH), total triiodothyronine (TT3), total thyroxin (TT4) free T3 (fT3), free T4 (fT4), and insulin were assessed by enzyme-linked immunoassays (ELISA). Fasting plasma glucose (FPG) and HbA1c were measured by glucose oxidase and low-pressure cation exchange chromatography. Homeostasis model of assessment (HOMA-IR) was employed to assess the level of insulin resistance; fT3/fT4 ratio was calculated. Anthropometric measurement and habits were recorded.ResultsMarked hyperinsulinemia and insulin resistance were observed in IGT subjects. Serum TT3 and fT3 levels were significantly low in the IGT as compared to normal glucose-tolerant (NGT) controls. TT4 and TSH were higher in IGT subjects as compared to control subjects. There was a significant positive correlation of TSH with BMI only in the control group (r = 0.351; P < 0.05). Correlation of insulin with TT3, fT3,and TSH was significant (P < 0.05) in IGT subjects. A significant low fT3/fT4 ratio was observed in IGT subjects as compared to NGT subjects (P < 0.01).In multiple regression analysis, TSH, TT4 and fT3 contributed significantly to the variance of fasting insulin and insulin resistance in IGT subjects.ConclusionHyperinsulinemia and insulin resistance are associated with low T3/T4 ratio in pre-diabetic euthyroid Pakistani subjects.